is at risk. half the north polar ice cap has disappeared. look at superstorm sandy here. look at the 60% of the u.s. in drought. last year the hottest year in u.s. history. we have to stop this. we have to arrest it. >> the single biggest reason for the decline of co2 emissions in the united states or the decline in the rate of increase has been the substitution of natural gas and sort of coal. because of fracking, natural gas has become cheap enough that we're replacing coal. in fact, we are now doing better than the european union in terms of meeting targets. i've heard you on the subject and it feels to me like you're still very -- you're on the fence on the issue of fracking. shouldn't you be more fully in favor of it with regulations and with protections because it is almost everywhere replacing coal and that is a big net plus in terms of co2 emissions. >> we have to be careful in measuring the global warming impact of the strategies that we choose. if you look at the latest satellite pictures of north america, there's a new ball of light as large as chicago in rural north dakota.